1. Field of the Invention
The present invention relates to a method and system for reducing power consumption in a coded railway track circuit. More particularly, the invention relates to a method and system for placing a coded railway track circuit apparatus into a reduced power, sleep mode during periods of low vehicle activity.
2. Background Information
In the art of railway signaling, traffic flow through signaled territory is typically directed by various signal aspects appearing on wayside indicators or cab signal units located on board railway vehicles. The vehicle operators recognize each such aspect as indicating a particular operating condition allowed at that time. Typical practice is for the aspects to indicate prevailing speed conditions.
For operation of this signaling scheme, the track is typically divided into cascaded sections known as “blocks.” These blocks, which may be generally as long as about two to about five miles in length, are electrically isolated from adjacent blocks by typically utilizing interposing insulated joints. When a block is unoccupied, track circuit apparatus connected at each end are able to transmit signals back and forth through the rails within the block. Such signals may be coded to contain control data enhancing the signaling operation. Track circuits operating in this manner are referred to as “coded track circuits.” One such coded track circuit is illustrated in U.S. Pat. No. 4,619,425. When a block is occupied by a railway vehicle, shunt paths are created across the rails by the vehicle wheel and axle sets. While this interrupts the flow of information between respective ends of the block, the presence of the vehicle can be positively detected.
U.S. Pat. No. 5,465,926 discloses a coded track circuit repeater having a standby mode. The coded railway track circuit apparatus has the capability of operating during periods of low vehicle activity in a reduced power standby mode. This is accomplished by switching circuitry, which interrupts power to most of the components within the track circuit apparatus in response to the recognition by standby initiation circuitry of a preselected standby initiation signal. Power to fail-over indicators, which would normally be activated due to a power failure, is also interrupted by fail-over interrupt circuitry. During the standby mode, monitor circuitry remains active and awaits reception of a preselected wake-up signal. The wake-up signal may be a unique signal or a link-up signal such as is periodically transmitted by some coded track circuit units during periods when the block is occupied. For example, the wake-up signal is received by a hardware filter, which recognizes that a track message was received. Operation is limited to a single direction, with the intent being to wake-up an entire series of track circuit units between two control points. Hence, in order to initiate train movement, it is required to wake-up several track circuit units with an inherent and probably excessive time delay (e.g., several minutes, depending on the number of track circuits).
This places a coded railway track circuit apparatus into a reduced power standby mode during periods of low vehicle activity. When the wake-up signal is received, full power is restored, thus resuming normal operation. Operation of the fail-over systems is also then re-established. See, also, U.S. Pat. No. 5,145,131.
U.S. Pat. No. 5,459,663 discloses a cab signal apparatus and method. Various track relays are used to form a selection network, which picks the code rate that represents the speed at which the train must not exceed. To avoid a second train from following a first vehicle into a block, vital track relays cut off the cab signals in the track circuit immediately behind the train. The relay circuitry applies cab signals to the block in which the train is located, while removing the cab signal from the block behind the moving vehicle. To avoid interference between multiple cab signal units transmitting simultaneously and to conserve power, it is desirable to turn-off as many cab signal transmitters as possible in front of and behind the moving vehicle. It is also desirable to turn-off the cab signal unit in the block immediately following the vehicle to avoid having a second vehicle enter that block and erroneously receive the cab signal.
U.S. Pat. No. 6,144,900 discloses a linear array of N wireless nodes, in which each node can communicate with its K-nearest-neighbors and has a unique identification by which it can be addressed. The network of nodes, in a preferred embodiment, constitutes a train with a clearly designated head-node in the lead locomotive at one end of the train, the other nodes of the network being specific cars of the train. The last car in the train is the end-of-train. Each node conserves battery power by enabling the radio to be in a powered-down or “sleep mode” and by reducing the duty cycle of the communication receiver portion of the radio.
U.S. Pat. No. 6,175,784 discloses a remotely operable rail car status monitor and control system, which includes a plurality of handbrake sensor and release monitors (HSRMs) configured for radio frequency (RF) communication with a handheld data terminal (HDT). A wake-up receiver is configured to receive wake-up commands from the HDT. The wake-up command is a single pulse capable of simultaneously “waking up” all the HSRMs within its range. Upon the detection of a wake-up command by the receiver, a microcontroller transitions from its Sleep state to its Normal state. The microcontroller can be programmed to transition from its Sleep state to its Normal state when motion greater than a slid wheel threshold level is sensed and a handbrake sensor indicates that a handbrake is in its applied state.
U.S. Pat. No. 6,276,542 discloses a transit system in which on-board computers (OBCs) of personal vehicles (PVs) communicate with a Master computer for a controlled roadway, providing a range of functions. Communication between the Master and the OBCs is wireless through a leased or dedicated cell network. The OBCs for active PVs are preferably never turned off, but rather put into a sleep mode. The Master may wake up any OBC within its communication range, and update data and functions with that OBC.
European Patent Application No. EP0748084 discloses a mode of communication for asset tracking units, which mode involves communication between a central station and individual tracking units using a primary satellite communication link. A secondary “mutter” mode of communication conserves power and employs local communication between the tracking units as opposed to direct satellite communication with the central station.
European Patent Application No. EP0748085 discloses a multiple load tracking system employing a global positioning system in which a master unit sleeps until a slave unit polling time.
German Patent Application No. DE019830053 discloses a train monitoring device employing wagon communication devices linked to an onboard computer for a locomotive and each wagon of the train. The wagon communication devices communicate with a monitoring center via a long distance communication link and with one another via a short distance communication link. Polling of the data is provided by each wagon communication device, which is normally held in a sleep mode.
Hence, there is room for improvement in methods and systems for reducing power consumption in a coded railway track circuit.